The chlor-alkali industry has used three processes for the production of chlorine, hydrogen, and caustic soda from brine: a mercury cell process, a diaphragm cell process, and a membrane cell process. The mercury cell process and the diaphragm cell process can both generate hazardous wastes that can include mercury or asbestos, and thus are often disfavored.
The membrane cell process utilizes a membrane which allows sodium ions to pass into the cathodic compartment where a reaction with hydroxyl ions can form caustic soda. The performance of the membrane used in the cell will deteriorate over time and possibly result in undesirable effects that can include an increase of cell voltage, decreased caustic current efficiency, and an increase in power consumption.
Replacing the membrane is often a costly and labor intensive process that can require significant down-time for the membrane cell and result in substantial production losses. As such, there is a need in the chlor-alkali industry for alternatives to replacing a cell membrane, while at the same time providing an opportunity for a reduction in production costs, a performance improvement, an increase in production rate, or a prolongation of the membrane's operational lifetime.